The present invention generally concerns a method for operating an integrated image sensor. More particularly, the present invention concerns a method for operating an integrated image sensor using CMOS technology. Such CMOS image sensors are intended, in particular, for making integrated photographic and video devices.
As a result of current integration technologies, it is possible to make an operational image capturing device in integrated form. Such an integrated image capturing device incorporates, on the same chip, a photo-sensor component formed of an assembly of photo-sensor elements typically organised in the form of a matrix, and a processing component intended to capture images and read the data picked up by the photo-sensor component.
Traditionally, integrated image capturing devices rely on charge transfer techniques. According to these techniques, photo-generated charges are collected and transferred in a determined manner. The most commonly used charge transfer techniques use CCD (charge-coupled devices) or CID (charge injection devices) components. Although these devices using these components have found numerous commercial applications, they nonetheless have serious drawbacks. In particular, these components rely on non standard manufacturing techniques, and in particular standards incompatible with standard CMOS manufacturing processes. Such components thus constitute obstacles, in terms of cost and ease of manufacturing, to the total integration of image sensors.
As a complement to the aforementioned techniques, a concept has been developed around the use of p-n semiconductor junctions as photo-sensor elements, these junctions being commonly called photodiodes. The essential advantage of such elements is their perfect compatibility with standard CMOS manufacturing processes. Thus, solutions relying on photodiodes as photo-sensor elements are known from the prior art, in particular from the document “A Random Access Photodiode Array for Intelligent Image Capture” by Orl Yadid-Pecht, Ran Ginosar and Yosi Diamand, IEEE Transactions on Electron Devices, Vol. 38, no. 8, August 1991, pp 1772–1780, incorporated here by reference.